Bumblebees - LS
With over 250 known species, the Bumblebee - or Bumble Bee - is a member belonging to the genus Bombus and the family ''Apidae. Primarily found in in the Northern Hemisphere, the bumblebees live in colonies with approximately 50 other members. Thermoregulation Background Bumblebees, much like any other 'cold-blooded' individual, are classified as ectotherms - an animal that has no means to regulate their body temperature hence is dependent on external sources for heat. However bumblebees have particularly well developed thermoregulatory behaviours, which is essential for bees to fly, to forage and to incubate their young. This is important as it allows their body temperature to adjust to a range of varying environmental conditions. Circulatory System The overall thermoregulation in bees is achieved by an alternating counter-current circulation which controls and regulates the blood circulation in the thorax and the abdomen. The heart of the bumblebee pumps blood from the abdomen to the thorax and the blood empties into the body cavity. The movements of the diaphragm forces the blood in the body cavity into the abdomen. At the petiole, cool blood passing from the abdomen to the heart passes warm blood flowing from the body cavity to the thorax. Due to the alternating pulses of the warm blood and cold blood, there is little heat exchanged and lost. Thermoregulation Mechanisms Bumblebees have a variety of thermoregulatory mechanisms which allow the to control their body temperature. It is most important for them to circulate their blood between the thorax and the abdomen to exercise minimal heat loss. '''No-Shake Shivers' This rapid mechanism occurs in insects just before they take off in flight. The bees warm up by producing their own heat - from basking in the sun - to increase the body temperature and warm their 'flight muscles'. During warm up, the flight muscles in bumblebees contract and heat from the thorax is transferred to the abdomen by separating warm and cool blood. This stimulates a shiver in the bees which allows the bees to preserve energy as well as maintain a high and stable body temperature during foraging which allows them to move between flowers more easily and quickly. While in hot conditions, bumblebees are able to warm up within seconds, in colder temperatures the warm up may take up to several minutes. Heart Loops In bumblebees, the heart loops down through a narrow petiole which ensures warm blood from the thorax must passes backwards through the petiole and come into close contact with cool blood flowing forward from the abdomen, creating a counter-current heat exchanger. This is important as it restricts the flow of heat from the core of the body so less heat is lost, which is essential in colder environments. ' Bumble Beats ' Another mechanism which bumblebees use in cold environments is their 'fur coat' which helps regulate the body temperature, as they cut heat loss by at least half. Incubating the Young The mechanism 'bumble beats' is also used my queen bumblebees to incubate the young. Similar to a bird, the queen bumblebee heats her abdomen during the incubation period, and it is through direct body heat she is able to heat the brood of young bumblebees.